1. Field of the Invention
The present invention relates to an X-ray imaging apparatus with a detachable battery mounted thereto.
2. Description of the Related Art
X-ray imaging, in which X-rays are applied to a subject to detect the intensity distribution of the X-rays transmitted through the subject to obtain an X-ray image of the subject, is widely utilized in the medical and industrial fields. Historically, the first system for obtaining an X-ray image was using the film-screen method, in which a photosensitive film having captured visible light emitted from an X-ray sensitive rare earth phosphor is chemically developed and visualized. The technological innovations thereafter have produced various systems. Among them is an imaging apparatus (Flat Panel Detector (FPD)) using a planar sensor to which a semiconductor processing technique is applied and in which pixels consisting of minute photoelectric conversion elements and switching elements are arranged in a lattice-like fashion. This apparatus is advantageous in that due to its much larger dynamic range as compared with that of conventional photosensitive films, it can obtain a stable X-ray image even if the X-ray exposure amount fluctuates, and that since it requires no chemical processing, it can quickly obtain an X-ray image.
From the viewpoint of form, the X-ray imaging apparatuses can be classified into an installation-type one that can be installed at a predetermined place such as an ordinary shooting room, and a portable one that can be freely carried about. In recent years, there has been an increasing demand for the portable X-ray imaging apparatus (hereinafter referred to as the “electronic cassette” or just the “cassette.”)
In a conventional electronic cassette, a control unit is electrically connected to a cable for supplying power from the outside. Thus, the treatment of the cable is troublesome, which obstructs handling of the electronic cassette; further, a surplus portion of the cable constitutes an obstacle. Further, in a clean (sterilized) environment such as an operation room, it is necessary to prevent the imaging system including the cable from coming into contact with an open (not sterilized) area such as the floor surface.
In view of this, a wireless cassette has recently been developed, in which the power supply cable has been done away with and which contains a battery instead; this novel cassette is expected to achieve a marked improvement of freedom degree in X-ray imagining.
This cassette requires attachment/detachment of the battery in order to perform charging and to replace the battery with a new one; however, when the driving of the cassette cannot be stopped as in the case where an X-ray image is being obtained or in the case where an image is being transferred to a control unit, the attachment/detachment of the battery must be restrained. A pertaining technique is discussed in Japanese Patent Application Laid-Open No. 2007-333380 and Japanese Patent Application Laid-Open No. 2009-53661.
It should be noted, however, that the wireless cassette is to be carried about in use; thus, it is requisite for the battery to be reliably retained even when a shock expected in normal condition of use is received such as vibration or dropping or when the cassette is inserted or drawn into or out of a gap between the subject and the bed. On the other hand, if the frequency of battery attachment/detachment is taken into consideration, it is important, from the viewpoint of improving the feel of use of the cassette, that the lock mechanism requires no special tool, enabling the operator to operate the cassette relatively easily.